Coacervation of copolymer of diallyldimethylammonium chloride and sodium styrenesulfonate aqueous solution

Coacervate behavior of polyelectrolyte complexes has been studied by many papers. Few studies have focused on the coacervate behavior of amphoteric polymer. In this study, amphoteric copolymer of diallyldimethylammonium chloride (DM) and sodium styrenesulfonate (SS) (the copolymer was noted as DMS) was synthesized with the mole content of SS to DM ranged from 0 to 10%. Firstly, DMS was characterized by static light scattering, FTIR, ¹H-NMR, TGA and DSC. Then, its phase and coacervate behaviors were studied. Turbidity was utilized as an indicator for the coacervate formation. It was found that when the SS content was more than 4 mol%, DMS coacervate would be formed in deionized water at a certain concentration. Temperature and pH have no effect on the formation of DMS coacervate. Meanwhile, salts has a great influence on the DMS coacervation. Unlike the results of the other polyelectrolyte complexes, Na₂SO₄, Na₂HPO₄, NaCOOCH₃, sodium citrate and NaI cannot prevent the DMS coacervate formation. However, the addition of NaCl, NaNO₃, NaBr and NaSCN can prevent the coacervate formation. The influence cannot be described by Hofmeister-like behavior. Results of surface tension and fluorescence spectrum presented that the driving forces to formation of DMS coacervate are the electrostatic interaction and the intermolecular hydrophobic interaction.     

Fabrication and sustained release properties of porous hollow silica nanoparticles

MCM-41-type mesoporous silica nanospheres(MSN) have been prepared using n-cetyltrimethylammonium bromide(CTAB) as a soft template.The pseudo-moire' rotational pattern inside the MSN results in many interior defects.Hollow mesoporous silica(HMS) spheres were synthesized by solvent extraction of the template from MSN.The morphology and structure of MSN and HMS were studied by TEM,XRD and nitrogen sorption techniques.A model drug,bromocresol green dye,was packed inside different regions of HMS through impregna...     

用离子液前驱体合成高荧光性能的ZnO和CdS纳米材料

合成了含Cd和Zn的离子液,使其提供金属离子,与Na2S反应制备离子液包裹的半导体纳米材料．X射线衍射和透射电子显微镜分析结果显示：在Cd离子液与Na2S反应中,得到的是尺寸在5～6nm、离子液包裹CdS纳米晶,而在Zn的体系中,最终产物为尺寸在1μm左右六方盘形貌的ZnO颗粒．用热力学和结晶动力学详细讨论了造成Cd和Zn体系在反应条件相同时,产物的形貌和结构差别的原因．荧光性质的测试结果表明：该方法制备的ZnO和CdS纳米粒子具有很好的荧光性能．     

Shape-controlled solvothermal synthesis of bismuth subcarbonate nanomaterials

Much effort has been devoted to the synthesis of novel nanostructured materials because of their unique properties and potential applications. Bismuth subcarbonate ((BiO)₂CO₃) is one of commonly used antibacterial agents against Helicobacter pylori (H. pylori). Different (BiO)₂CO₃ nanostructures such as cube-like nanoparticles, nanobars and nanoplates, were fabricated from bismuth nitrate via a simple solvothermal method. The nanostructures were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that the solvents and precursors have an influence on the morphologies of (BiO)₂CO₃ nanostructures. The possible formation mechanism of different (BiO)₂CO₃ nanostructures fabricated under different conditions was also discussed.     

Synthesis and antitumor evaluation of C3/C3 fluoroquinolone dimers(Ⅰ):Tethered with a fused heterocyclic s-triazolo[2,1-b][1,3,4]thiadiazole

<正>Five C3/C3 fluoroquinolone dimers tethered with a fused heterocyclic ring of s-triazolo[2,1-b][1,3,4]thiadiazole derived from antibacterial quinoiones were synthesized and characterized,and their in vitro antitumor activity against L1210,CHO cell lines was evaluated via the respective IC_(50) values.     

Electrochemical impedance analysis of nanoporous TiO_2 electrode at low bias potential

<正>TiO_2 colloid was prepared by the sol-gel method and was bladed on transparent conduction glass to made nanoporous electrode. The impedance performance of TiO_2 electrode was studied at various bias potential.A simplified equivalent circuit was proposed to investigate the charge transport impedance of TiO_2 film and good fitting results were obtained.     

Facile synthesis of mesoporous silica nanoparticles with controlled morphologies using water–acetone media

Mesoporous silica nanoparticles with controlled morphologies including nanococoons, nanorods and nanospheres have been synthesized in water–acetone media at room temperature using cetyltrimethylammonium bromide (CTAB) as the template. The obtained nanoparticles generally show hexagonal-like mesoporous structures with average pore size ranging from 2.7 to 3.3 nm and surface area from 806 to 1055 m²/g, respectively. It was found that the changes in water-to-acetone molar ratios have a dramatic impact on the morphologies of the mesoporous silica with different surface roughness, probably due to the solvent influence on the rate of the hydrolysis of tetraethoxy silane (TEOS) and the polymerization of inorganic species. Interestingly, the morphology of the mesoporous silica products can be controlled in shape from nanococoons to nanorods to nanospheres just by decreasing the water-to-acetone molar ratio from 75 to 30 to 15, respectively. From transmission electron microscopy (TEM) images, it was observed that mesoporous parallel channels run along the short axis in some areas in the nanorods, whereas the radially arranged mesopore channels are present in the nanospheres. Additionally, hydrothermal treatment leads to rougher surfaces while retaining the morphologies and nanostructures of these mesoporous silicas.     

Preparation and Characterization of Aligned PLLA/PCL/HA Composite Fibrous Membranes

Aligned poly(L-lactide) (PLLA)/poly(?-caprolactone) (PCL)/hydroxyapaite (HA) composite fibrous membranes were fabricated by electrospinning. Their morphology, thermal stability, mechanical properties, hydrophilic properties and biocompatibility were investigated. The electrospun fibers are highly aligned and the HA are oriented along the fiber axis. When HA are incorporated, the PLLA/PCL/HA composite fibers become thinner due to the increased conductivity. In addition, the aligned HA reinforce the electrospun fibrous membranes. The larger porosity and higher hydrophilic properties induced by HA in the electrospun fibers have improved the degradation of the PLLA/PCL/HA fibrous membranes which have no toxic effect on proliferation of adipose-derived stem cells.     

小波分析中一个逆问题

本文证明:如果来自多尺度分析(伸缩因子为矩阵)的小波是标准正交的,那么相对应的尺度函数也是标准正交的,其中函数f_s(x)∈L~2(R~n)(s=1,2,…,r,r是正整数)的标准正交性是指f_s(x)的整平移所构成的函数族为L~2(R~n)的标准正交系。结果表明,如果我们想从多尺度分析出发构造正交小波,那么该多尺度分析必须有正交尺度函数。